add all clear values to summary

Author: keithamus

css-page-floats-3/Overview.bs

@@ -464,7 +464,7 @@ The 'clear' property</h2>
 
   <pre class="propdef">
     Name: clear
-    Value: inline-start | inline-end | block-start | block-end | left | right | top | bottom | none
+    Value: inline-start | inline-end | block-start | block-end | left | right | top | bottom | both-inline | both-block | both | none
     Initial: none
     Applies to: block-level elements, floats, regions, pages
     Inherited: no